Environments such as homes and offices require numerous switches for actuating devices such as lamps and HVAC equipment. A conventional home thus includes costly wiring between all the switch controls and the various power sinks such as lights, heaters, computers, radio and TV sets, and so on. In addition to the cost associated with wires, maintenance and installations, positioning of the switches and fixtures need to be predetermined at the time of installation. In mobile environments such as cars other factors like the weight of the copper saved in the wiring of the switches is, in and of itself, enough motivation for having a wireless network of passive switches. Copper wiring is not only expensive but also heavy; saving copper results in lower manufacturing cost and better fuel economy.
Inside cars and similar environments, the position of switches, control knobs and sensors is crucial in maintaining functional, user-friendly operation and esthetically appealing instrumentation layout. The esthetic aspects of such placements as well as the practical difficulties in providing wired connections to all such switches and sensors, e.g. through the steering wheel and hard to reach structures, present considerable design difficulties.
To eliminate the cost of installing wires between the switch and the device being actuated by the switch, various wireless switches have been developed. Similarly, wireless sensors have been developed to eliminate the need for wires between the sensors and the control systems requiring information from the sensors. One type of conventional wireless switches uses a narrowband data link to power up the switch such that the switch can manipulate the narrowband incident signal or field to convey the switch state accordingly. Such wireless switches include traditional passive radios such as backscattering or magnetically coupling RFID transponders.
Another group of solutions use a transducer to convert the mechanical energy imparted by the user actuating the switch into the required electrical energy needed for generating a narrowband RF carrier, see e.g. U.S. Pat. No. 7,245,062. But both conventional narrowband RFID approaches and transducer approaches suffer from multipath and sensor collisions.
Accordingly, there is a need in the art for improved wireless switches and sensors.